Field of the Invention
The invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device and a manufacturing method thereof capable of preventing an issue caused by difference in pattern density.
Description of Related Art
In the current semiconductor process, an isolation structure is generally formed in a substrate to define a device region having a plurality of active areas and a peripheral region. As the size of devices continues to be smaller, the layout area of the device region also becomes smaller. As a result, a greater difference in pattern density results on the substrate, and the difference in pattern density becomes an issue in a subsequent process.
The effect from the difference in pattern density is more significant at the boundary of the device region and the peripheral region. For instance, when films are stacked on the active areas adjacent to the boundary of the device region, film stress caused by the difference in pattern density is generated. Moreover, during film deposition, thermal stress is also generated in the above regions. Due to the film stress and thermal stress, the films on the active areas adjacent to the boundary of the device region are readily tipped, and therefore a subsequent process is affected.